Low viscosity gear lubricants

ABSTRACT

A lubricant composition of 40 to 95% of an oil having a kinematic viscosity at 100° C. of 3 to 7.5; 0.3 to 2% of an amine salt of a phosphorus compound obtained by reacting phosphorus pentasulfide with one or more alcohols having 4 to about 13, or 4 to 8, or 6, carbon atoms, with an alkylene oxide, and further with phosphorus pentoxide, and salting the resulting material with one or more amines having 2 to 20 or 12 to 24 carbon atoms; and an active-sulfur containing agent in an amount to provide 0.5 to 7% sulfur to the composition provides good wear protection to gears at a relatively low viscosity of the composition.

BACKGROUND

The disclosed technology relates to lubricants, especially for gears orbearings, having a relatively low viscosity yet having good antiwearperformance by including in the lubricant a certain amine salt of aphosphorus compound (or mixtures thereof).

Moving mechanical parts generally need to be lubricated. Among surfacesor parts requiring lubrication are gears or bearings, such as those thatmay be found in machinery or vehicles such as in drivelines of vehicles(e.g., transmissions, gear boxes, axles, differentials). An axleassembly may typically comprise one or more gears and one or morebearings. In recent years the lubrication and transportation industryhave been moving toward requiring gear oils of lower viscosity in orderto provide improved efficiency and fuel economy, for instance, due toreduced fluid drag and energy loss. Lubricants of reduced viscosity,however, tend to provide reduced lubricant film thickness between thelubricated parts, and such systems thus become increasingly dependent onboundary film protection, that is, chemical protection of the surfacesprovided by additive chemistry within the lubricant, as distinct fromthe lubrication provided by the bulk of the lubricant.

Film thickness may be described in terms of λ ratio, which is defined asthe ratio of fluid film thickness to the composite surface roughness ofthe surfaces being lubricated (r₁ ²+r₂ ²)^(1/2). The λ ratio will dependon the particular surfaces involved, the pressure applied between thesurfaces, and the viscosity of the lubricant, less viscous lubricantstending to provide systems having a lower λ. It is often considered thatwhen λ is 3 or greater, full-film, or thick film, or hydrodynamic,lubrication will prevail. When λ is between 1.2 and 3, the lubricationis often referred to as mixed or thin film, and when λ is less than 1.2,boundary lubrication will prevail. That is, in the case of boundarylubrication, over a certain portion of the lubricated surface there maybe direct physical contact between the surfaces (or between the chemicalcoatings on the surfaces) with little or no bulk lubricant separatingthe surfaces in those areas. It is for lubricating conditions where λ is2 or less, 1.8 or less, or 1.5 or less, or 1.2 or less, that lubricatingchallenges become more severe.

The wheels of an on-highway and/or off-highway vehicle can be driven bya final drive axle unit that splits the torque received from the inputshaft between the wheels by means of a gear set inside a gear housing ofthe final drive unit. The gears in the final drive can be of the typeincluding but not limited to spiral bevel, hypoid, spur and helical orcombination thereof. In one example the gear arrangement can be adifferential gear arrangement. These gears require lubrication. Amongthe functions of the gear lubricant are to provide adequate protectionagainst wear, scuffing, and micropitting and to provide for seal,rubber, and composite material capability, while providing acceptableoxidation stability and cleanliness during the service life of the gearequipment. Therefore, there is need for a gear lubricating compositionhaving a relatively low viscosity while providing at least one of wearprotection and seal, rubber and composite material capability.

U.S. Pat. No. 3,197,405, Le Suer, Jul. 27, 1965, discloses phosphorus-and nitrogen-containing compositions useful as additives in lubricatingcompositions. They may be prepared by reacting a hydroxyl-substitutedtriester of a phosphorothioic acid with an inorganic phosphorus reagentand neutralizing with a hydrocarbon- or hydroxy-substituted hydrocarbonamine having about 4 to about 30 carbon atoms.

U.S. Pat. No. 8,865,633, MacPherson et al., Oct. 21, 2014 (earlierpublished as US 2013/0053288, Feb. 28, 2013) discloses gear oilcompositions including a major amount of a base oil having a lubricatingviscosity, a polysulfide extreme pressure agent, and a reaction productof an acylated copolymer and a polyamine. An antiwear agent may bepresent which may include, among others, an organic ester of phosphoricacid, phosphorous acid, or an amine salt thereof. The base oil is about55 weight percent to less than 100 weight percent bright stock base oil.In an example, the gear oil formulation had a viscosity grade of 80W-90.

The lubricating composition of the invention is suitable for lubricantsin a variety of mechanical devices, including automobiles, trucks, andother equipment such as a manual transmission, an automatictransmission, an automated manual transmission, a continuously variabletransmission, a dual clutch transmission, a farm tractor transmission, atransaxle, a heavy duty power-shift transmission, and wet brakes) aswell as final drive axles gearing systems and gears such as anautomotive gear and a farm tractor gear.

The disclosed technology solves the problem of providing wear protectionfor gears which are lubricated with a relatively low viscositylubricant, and/or under a regime of λ≤2, by including in the lubricantan amine salt of a phosphorus compound or mixtures thereof, as describedin greater detail herein.

SUMMARY

The disclosed technology provides a lubricant composition comprising:(a) an oil having a kinematic viscosity at 100° C. by ASTM D445 of 3 to7.5 or 3.6 to 6 or 3.5 to 5 mm²/s; (b) 0.3 to 2 percent by weight of anamine salt of a phosphorus compound, or mixtures thereof, obtained byreacting phosphorus pentasulfide with one or more alcohols having 4 to13, or 4 to 8, or 6, carbon atoms, with an alkylene oxide, and furtherwith phosphorus pentoxide, and salting the resulting material with oneor more amines having 2 to 20 or 12 to 24 carbon atoms; and (c) asulfurized olefin in an amount to provide about 0.5 to about 7, or about0.5 to about 1.5, or about 1.5 to about 2, or about 3 to about 5, orabout 2 to about 3, percent by weight sulfur to the composition; whereinsaid composition has a kinematic viscosity at 100° C. by ASTM D445 of upto 7.5, or 3.5 to 7.0, or 4 to 6.5, or 4 to 6 mm²/s.

The disclosed technology also provides a method of lubricating a gearcomprising supplying thereto the lubricant composition described herein.

DETAILED DESCRIPTION

Various preferred features and embodiments will be described below byway of non-limiting illustration.

The lubricant composition of the disclosed technology comprises as onecomponent, an oil of lubricating viscosity. Such oils include naturaland synthetic oils, oil derived from hydrocracking, hydrogenation, andhydrofinishing, unrefined, refined, and re-refined oils and mixturesthereof. Unrefined oils are those obtained directly from a natural orsynthetic source generally without (or with little) further purificationtreatment. Refined oils are similar to the unrefined oils except theyhave been further treated in one or more purification steps to improveone or more properties. Purification techniques are known in the art andinclude solvent extraction, secondary distillation, acid or baseextraction, filtration, percolation and the like. Re-refined oils arealso known as reclaimed or reprocessed oils, and are obtained byprocesses similar to those used to obtain refined oils and often areadditionally processed by techniques directed to removal of spentadditives and oil breakdown products.

Natural oils useful in making the inventive lubricants include animaloils, vegetable oils (e.g., castor oil), mineral lubricating oils suchas liquid petroleum oils and solvent-treated or acid-treated minerallubricating oils of the paraffinic, naphthenic or mixedparaffinic-naphthenic types and oils derived from coal or shale ormixtures thereof.

Synthetic lubricating oils are useful and include hydrocarbon oils suchas polymerized and interpolymerized olefins (e.g., polybutylenes,polypropylenes, propyleneisobutylene copolymers); poly(l-hexenes),poly(l-octenes), poly(l-decenes), and mixtures thereof; alkyl-benzenes(e.g. dodecylbenzenes, tetradecylbenzenes, dinonyl¬benzenes,di-(2-ethylhexyl)-benzenes); polyphenyls (e.g., biphenyls, terphenyls,alkylated polyphenyls); diphenyl alkanes, alkylated diphenyl alkanes,alkylated diphenyl ethers and alkylated diphenyl sulfides and thederivatives, analogs and homologs thereof or mixtures thereof. Othersynthetic lubricating oils include polyol esters (such asPriolube®3970), diesters, liquid esters of phosphorus-containing acids(e.g., tricresyl phosphate, trioctyl phosphate, and the diethyl ester ofdecane phosphonic acid), or polymeric tetrahydrofurans. Synthetic oilsmay be produced by Fischer-Tropsch reactions and typically may behydroisomerized Fischer-Tropsch hydrocarbons or waxes. In one embodimentoils may be prepared by a Fischer-Tropsch gas-to-liquid syntheticprocedure as well as other gas-to-liquid oils.

Oils of lubricating viscosity may also be defined as specified in theAmerican Petroleum Institute (API) Base Oil InterchangeabilityGuidelines (2011). The five base oil groups are as follows: Group I(sulfur content >0.03 wt %, and/or <90 wt % saturates, viscosity index80 to less than 120); Group II (sulfur content <0.03 wt %, and >90 wt %saturates, viscosity index 80 to less than 120); Group III (sulfurcontent <0.03 wt %, and >90 wt % saturates, viscosity index ≥120); GroupIV (all polyalphaolefins (PAOs)); and Group V (all others not includedin Groups I, II, III, or IV). The oil of lubricating viscosity may alsobe an API Group II+ base oil, which term refers to a Group II base oilhaving a viscosity index greater than or equal to 110 and less than 120,as described in SAE publication “Design Practice: Passenger CarAutomatic Transmissions”, fourth Edition, AE-29, 2012, page 12-9, aswell as in U.S. Pat. No. 8,216,448, column 1 line 57.

The oil of lubricating viscosity may be an API Group IV oil, or mixturesthereof, i.e., a polyalphaolefin. The polyalphaolefin may be prepared bymetallocene catalyzed processes or from a non-metallocene process. Theoil of lubricating viscosity may comprise an API Group I, Group II,Group III, Group IV, Group V oil or mixtures thereof. Often the oil oflubricating viscosity is an API Group I, Group II, Group II+, Group III,Group IV oil or mixtures thereof. Alternatively the oil of lubricatingviscosity is often an API Group II, Group II+, Group III or Group IV oilor mixtures thereof. Alternatively the oil of lubricating viscosity isoften an API Group II, Group II+, Group III oil or mixtures thereof. Inone embodiment, the oil of lubricating viscosity comprises apolyalphaolefin. In one embodiment, the oil of lubricating viscositycomprises a Group III oil or a Group III+ oil (where Group III+ is asubset of Group III oils, having a higher viscosity index such as ≥130).In one embodiment the poly alpha olefin has a kinetic viscosity at 100°C. of 3 to 7.5 (ASTM D445).

The oil of lubricating viscosity, as used in the disclosed technology,will have a kinematic viscosity at 100° C. (“KV_100”) as determined byASTM D445 of 3 to 7.5 mm²/s or alternatively 3.3 to 6.5, or 3.6 to 6, or3.5 to 5, mm²/s. This viscosity value or range will be the viscosity ofthe entire oil of lubricating viscosity component, whether it be an oilfrom a single source and a single grade or a mixture of oils, but doesnot include any contribution to viscosity of any additives such asviscosity modifiers. In one embodiment the presence of small amounts ofdiluent oil which may be conventionally provided along with some of theadditive components to be described later is not included in thedetermination of the KV_100; alternatively, if desired, the contributionof such diluent oils may be included. In either event, the KV_100 of theoil (base oil) component is less than about 7.5 mm²/s, which is arelatively low value for a lubricant designed for use as a gearlubricant.

The KV_100 of the base oil, above, is one contributor to the KV_100 ofthe finished lubricant containing the additional components andadditives described herein. Presence of additional components may resultin an increase in the KV_100 of the finished lubricant, particularly ifthose components, such as polymeric components, themselves have arelatively higher KV_100. The overall KV_100 of the lubricantcomposition may be up to 8.5 or to 8.0 or to 7.5, such as 3.5 to 7.0 or4 to 6.5, or 4 to 6 mm²/s.

The amount of the oil of lubricating viscosity present is typically thebalance remaining after subtracting from 100 weight percent the sum ofthe amount of the additives as described herein. Typical amounts include40 to 95 percent by weight, or 45 to 90, or 50 to 80, or 55 to 75, or 58to 70, or 60 to 65 percent by weight.

The lubricating composition may be in the form of a concentrate and/or afully formulated lubricant. If the lubricating composition of theinvention is in the form of a concentrate (which may be combined withadditional oil to form, in whole or in part, a finished lubricant), theratio of the of components of the invention to the oil of lubricatingviscosity and/or to diluent oil include the ranges of 1:99 to 99:1 byweight, or 80:20 to 10:90 by weight.

Another component of the lubricant is an amine salt of a phosphorus acidester. This material can serve as one or more of an extreme pressureagent or a wear preventing agent. The amine salt of a phosphorus acidester includes phosphoric acid esters and salts thereof;dialkyldithiophosphoric acid esters and salts thereof; phosphites; andphosphorus-containing carboxylic esters, ethers, and amides; andmixtures thereof. In one embodiment the phosphorus compound comprises asulfur atom in the molecule. In one embodiment the amine salt of thephosphorus compound is ashless, i.e., metal-free (prior to being mixedwith other components).

The amine salt of the phosphorus acid ester may comprise any of avariety of chemical structures. In particular, a variety of structuresare possible when the phosphorus acid ester compound contains one ormore sulfur atoms, that is, when the phosphorus-containing acid is athiophosphorus acid ester. The thiophosphorus acid esters may be mono-or dithiophosphorus acid esters. Thiophosphorus acid esters are alsosometimes referred to as thiophosphoric acids. A thiophosphorus acidester may be prepared by reacting a sulfur and phosphorus compound withan alcohol. Suitable phosphorus compound include phosphorus sulfidessuch as phosphorus pentasulfide. Suitable alcohols include thosecontaining 4 to 13 carbon atoms, or 4 to 8, or 5 to 7, or 6 carbonatoms, including primary or secondary alcohols such as butyl, isobutyl,amyl, s-amyl, 2-ethylhexyl, hexyl, cyclohexyl, octyl, decyl and dodecylalcohols and isomers thereof, as well as any of a variety of commercialalcohol mixtures having similar numbers of carbon atoms, e.g., 8 to 10.In one embodiment the alcohol has 6 carbon atoms; in one embodiment thealcohol comprises or is 4-methylpentan-2-ol.

In one embodiment, the thiophosphorus acid ester is a monothiophosphoricacid ester or a monothiophosphate. Monothiophosphates may be prepared bythe reaction of a sulfur source with a dihydrocarbyl phosphite. Thesulfur source may, for instance, be elemental sulfur, or anorganosufide, such as a sulfur coupled olefin or a sulfur coupleddithiophosphate. The preparation of monothiophosphates is disclosed inU.S. Pat. No. 4,755,311 and PCT Publication WO 87/07638, which describemonothiophosphates, sulfur sources, and the process for makingmonothiophosphates. Monothiophosphates may also be formed in thelubricant blend by adding a dihydrocarbyl phosphite to a lubricatingcomposition containing a sulfur source, such as a sulfurized olefin. Thephosphite may react with the sulfur source under blending conditions(i.e., temperatures from 30° C. to 100° C. or higher) to form themonothiophosphate salt with an amine which is present in the blend.

In certain embodiments, the phosphorus-containing acid is adithiophosphoric acid or phosphorodithioic acid. The dithiophosphoricacid may be represented by the formula (RO)₂PSSH wherein each R isindependently a hydrocarbyl group containing 4 to 13 carbon atoms, suchas those derived from the alcohol listed above. Examples of R includeisobutyl, n-butyl, sec-butyl, the various amyl, n-hexyl, methylisobutylcarbinyl, heptyl, 2-ethylhexyl, isooctyl, nonyl, behenyl, decyl,dodecyl, and tridecyl groups. Illustrative lower alkylphenyl R groupsinclude butylphenyl, amylphenyl, and heptylphenyl. Examples of mixturesof R groups include 1-butyl and 1-octyl; 1-pentyl and 2-ethyl-1-hexyl;isobutyl and n-hexyl; isobutyl and isoamyl; 2-propyl and2-methyl-4-pentyl; isopropyl and sec-butyl; and isopropyl, and isooctyl.

The dithiophosphoric acid is further reacted with an epoxide and thisreaction product further reacted with a phosphorus pentoxide. Theepoxide is generally an aliphatic epoxide or a styrene oxide. Examplesof useful epoxides include ethylene oxide, propylene oxide, buteneoxide, octene oxide, dodecene oxide, and styrene oxide. The epoxides maybe aliphatic epoxides having from 2 to 12, or 3 to 6, or 3 or 4 carbonatoms. In one embodiment the alkylene oxide comprises 1,2-propyleneoxide. The dithiophosphoric acids, epoxides, inorganic phosphorusreagents, and methods of reacting the same are described in U.S. Pat.Nos. 3,197,405 and 3,544,465.

The following Examples P-1 and P-2 exemplify the preparation of usefulphosphorus acid esters.

Example P-1

Phosphorus pentoxide (about 64 grams) is added at about 58° C. over aperiod of about 45 minutes to about 514 grams of hydroxypropylO,O-di(4-methyl-2-pentyl)phosphorodithioate (prepared by reactingdi(4-methyl-2-pentyl)-phosphorodithioic acid with about 1.3 moles ofpropylene oxide at about 25° C.). The mixture is heated at about 75° C.for about 2.5 hours, mixed with a diatomaceous earth and filtered atabout 70° C. The filtrate contains about 11.8% by weight phosphorus,about 15.2% by weight sulfur, and an acid number of 87 (bromophenolblue).

Example P-2

A mixture of about 667 grams of phosphorus pentoxide and the reactionproduct of about 3514 grams of diisopropyl phosphorodithioic acid withabout 986 grams of propylene oxide at about 50° C. is heated at about85° C. for about 3 hours and filtered. The filtrate contains about 15.3%by weight phosphorus, about 19.6% by weight sulfur, and an acid numberof 126 (bromophenol blue).

Acidic phosphoric acid esters may be reacted with ammonia or an amine,including polyamines, to form an ammonium salt. The salts may be formedseparately and then the salt of the phosphorus acid ester may be addedto the lubricating composition. The amines which may be suitable for useas the amine salt include primary amines, secondary amines, tertiaryamines, and mixtures thereof. The amines include those with at least onehydrocarbyl group, or, in certain embodiments, two or three hydrocarbylgroups. The hydrocarbyl groups may typically contain 2 to 30 carbonatoms, or in other embodiments 8 to 26 or 10 to 20 or 13 to 19 carbonatoms.

Primary amines include ethylamine, propylamine, butylamine,2-ethylhexylamine, octylamine, and dodecylamine, as well as such fattyamines as n-octylamine, ndecylamine, n-dodecylamine, n-tetradecylamine,n-hexadecylamine, n-octadecylamine, and oleylamine. Other useful fattyamines include commercially available fatty amines such as “Armeen®”amines (products available from Akzo Chemicals, Chicago, Ill.), such asArmeen C, Armeen O, Armeen O L, Armeen T, Armeen H T, Armeen S andArmeen S D, wherein the letter designation relates to the fatty group,such as coco, oleyl, tallow, or stearyl groups.

Examples of suitable secondary amines include dimethylamine,diethylamine, dipropylamine, dibutylamine, diamylamine, dihexylamine,diheptylamine, methylethylamine, ethylbutylamine and ethylamylamine. Thesecondary amines may be cyclic amines such as piperidine, piperazine,and morpholine.

The amine may also be a tertiary-aliphatic primary amine. The aliphaticgroup in this case may be an alkyl group containing 2 to 30, or 6 to 26,or 8 to 24 carbon atoms. Tertiary alkyl amines include monoamines suchas tert-butylamine, tert-hexylamine, 1-methyl-1-amino-cyclohexane,tert-octylamine, tert-decylamine, tertdodecylamine,tert-tetradecylamine, tert-hexadecylamine, tert-octadecylamine,tert-tetracosanylamine, and tert-octacosanylamine.

Mixtures of amines may also be used in the invention. In one embodimenta useful mixture of amines is “Primene® 81R” and “Primene® JMT.”Primene® 81R and Primene® JMT (both produced and sold by Rohm & Haas)are mixtures of C11 to C14 tertiary alkyl primary amines and C18 to C22tertiary alkyl primary amines respectively.

Suitable hydrocarbyl amine salts of dialkyldithiophosphoric acid estersof the invention may be represented by the formula:

wherein R²⁶ and R²⁷ are independently hydrogen or hydrocarbyl groupssuch as alkyl groups; for the phosphorus acid ester, at least one of R²⁶and R²⁷ will be hydrocarbyl. R²⁶ and R²⁷ may contain 3 or 4 to 30, or 8to 25, or 10 to 20, or 13 to 19 carbon atoms. R²³, R²⁴, and R²⁵ can beindependently hydrogen or hydrocarbyl groups, such as alkyl branched orlinear alkyl chains with 1 to 30, or 4 to 24, or 6 to 20, or 10 to 16carbon atoms. These R²³, R²⁴, and R²⁵ groups can be branched or lineargroups, and in certain embodiments at least one, or alternatively two ofR²³, R²⁴, and R²⁵ are hydrogen. Examples of alkyl groups suitable forR²³, R²⁴, and R²⁵ include butyl, sec-butyl, isobutyl, tert-butyl,pentyl, n-hexyl, sec-hexyl, n-octyl, 2-ethylhexyl, decyl, undecyl,dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl,octadecyl, octadecenyl, nonodecyl, eicosyl groups and mixtures thereof.

In one embodiment the hydrocarbyl amine salt of an alkylthiophosphoricacid ester is the reaction product of a C₁₄ to C₁₈ alkylated phosphoricacid with Primene 81R™ (produced and sold by Rohm & Haas) which is amixture of C₁₁ to C₁₄ tertiary alkyl primary amines. Other amines whichmay be used include alkyl alkanol amines, dialkanolamines,trialkanolamines such as triethanolamines as well as borated amines asdescribed hereinbelow.

The amine salt of as used as this component in the present invention maythus comprise a C₈ to C₂₀ alkylamine salt of a mono- or di-alkylphosphate ester, or mixtures thereof. It will be understood by theskilled person that the amine salt of the thiophosphrus acid ester willtypically comprises a mixture of various individual chemical species.Reference herein to “an amine salt of a phosphorus compound,” used inthe description of component (b) herein will be understood by theskilled person to encompass mixtures of such compounds as may beprepared by the described syntheses.

The amount of the amine salt of the thiophosphorus acid ester in thelubricant can be 0.3 to 2 weight percent, or 0.4 to 1.9, or 0.5 to 1.8,or 0.7 to 1.7 weight percent. The amounts will be proportionally higherin a concentrate. The amount of said amine salt may also be an amount tocontribute 0.03 to 0.2 weight percent phosphorus to the lubricantcomposition, or alternatively 0.08 to 0.17, or 0.11 to 0.17 weightpercent.

One or more additional phosphorus compounds may also optionally bepresent, beside the amine salt of the thiophosphorus acid describedabove. They may provide a measure of additional antiwear performance, orthey may be present for other functional reasons. Some of these may beamine salts of phosphorus esters, but without the sulfur component ofthe above-described chemistry. Examples include amine salts ofdialkylphosphates such as a branched C8 amine salt of di-isooctylphosphate; phosphites such as dibutyl phosphite, di 16- or 18-carbonalkyl- or alkylene-phosphites (that is, in which the long carbon chainsmay optionally contain unsaturation); an amine salt of phosphoric acidoleyl esters; and phospholipids such as lecithins, e.g., boratedlecithins. The total amount of phosphorus in the lubricant compositionfrom all sources may be 0.03 to 0.30 weight percent, or 0.03 to 0.25, or0.03 to 0.21, or 0.05 to 0.21, or 0.08 to 0.30, or 0.08 to 0.25, or 0.08to 0.21, or 0.10 to 0.20, or 0.12 to 0.18 weight percent.

Component (c) is the sulfurized olefin, which may also be considered tobe an active sulfur containing compound. A definition of active sulfuris that the compound meets the definition of sulfur reactive with copperpowder at a temperature of 149° C. The test method for determiningactive sulfur is determined in the STANDARD TEST METHOD FOR ACTIVESULFUR IN CUTTING FLUIDS Designation: D 1662-69 (Reapproved 1979) as setforth by the American Society for Testing and Materials (ASTM).

A wide variety of sulfurized olefins can be utilized and these compoundsmay generally be represented by the formula RS_(x)R₁ wherein Srepresents sulfur, x is a whole number having a value of from 1 to about10, and R and R₁ may be the same or different organic groups derivedfrom olefins. The organic groups may be hydrocarbon groups orsubstituted hydrocarbon groups containing alkyl, aryl, aralkyl, alkaryl,alkanoate, thiazole, imidazole, phosphorothionate, or beta-ketoalkylgroups. The substantially hydrocarbon groups may contain othersubstituents such as halogen, amino, hydroxyl, mercapto, alkoxy,aryloxy, thio, nitro, sulfonic acid, carboxylic acid, or carboxylic acidester.

Specific examples of types of sulfurized olefins include alkyl oralkenyl sulfides and polysulfides, sulfurized carboxylic acid esterolefins, sulfurized ester olefins, sulfurized olefinic oil, and mixturesthereof. The preparation of such sulfurized olefins is described in theart.

The sulfurized olefin compounds utilized in the present invention can bealkyl sulfides such as dicetyl sulfide, diparaffin wax sulfide andpolysulfide, or cracked wax oleum sulfides. One method of preparing thealkyl sulfides includes the condensation of a chlorinated hydrocarbonwith an inorganic sulfide whereby the chlorine atom from each of twomolecules is displaced, and the free valence from each molecule isjoined to a divalent sulfur atom. Generally, the reaction is conductedin the presence of elemental sulfur.

Examples of dialkenyl sulfides are described in U.S. Pat. No. 2,446,072.These sulfides can be prepared by reacting an olefinic hydrocarboncontaining from 3 to 12 carbon atoms with elemental sulfur in thepresence of zinc or a similar metal generally in the form of an acidsalt. Examples of sulfides of this type include6,6′-dithiobis(5-methyl-4-nonene), 2-butenyl monosulfide and disulfide(the diisobutyl sulfides), and 2-methyl-2-butenyl monosulfide anddisulfide. Certain sulfurized isobutylenes may contain 40 to 45 weightpercent sulfur.

The sulfurized olefins include materials prepared by the reaction of anolefin (such as those containing 2 to 6 carbon atoms) or a lowermolecular weight polyolefin derived therefrom, with a sulfur-containingcompound such as sulfur, sulfur monochloride, sulfur dichloride,hydrogen sulfide, and combinations thereof.

The olefin is usually one in which each R is independently alkyl,alkenyl or aryl, or a corresponding substituted group. Monoolefinic anddiolefinic compounds, particularly the former, may be used, such asterminal monoolefinic hydrocarbons. Olefinic compounds having 3 to 30,or 3 to 16, or 9 or fewer, or 8 carbon atoms may be used.

Ethylene, isobutene, propylene, and oligomers thereof are especiallypreferred olefinic compounds. Of these compounds, isobutylene anddiisobutylene are particularly desirable because of their availabilityand the particularly high sulfur-containing compositions which can beprepared therefrom.

Another class of sulfurized olefins includes sulfurized aliphatic estersof an olefinic mono- or dicarboxylic acid. For example, aliphaticalcohols of from 1 to 30 carbon atoms can be used to esterifymonocarboxylic acids such as acrylic acid, methacrylic acid, or2,4-pentadienoic acid or fumaric acid, maleic acid, or muconic acidSulfurization of these olefinic esters is conducted with elementalsulfur, sulfur monochloride and/or sulfur dichloride.

Still another class of sulfurized olefin compounds which can be utilizedin the compositions of the invention are diester sulfides characterizedby the general formula ROOC(CH₂)_(x)—S_(y)—(CH₂)_(x)COOR wherein each xis independently 2 to 5; y is 1 to 6, such as 1 to about 3; and each Ris independently an alkyl group having 4 to 20 carbon atoms. The R groupmay be a straight chain or branched chain group that is large enough tomaintain the solubility of the compositions of the invention in oil.Typical diesters include the butyl, amyl, hexyl, heptyl, octyl, nonyl,decyl, tridecyl, myristyl, pentadecyl, cetyl, heptadecyl, stearyl,lauryl, and eicosyl diesters of thiodialkanoic acids such as propionic,butanoic, pentanoic, and hexanoic acids. Of the diester sulfides, aspecific example is dilauryl, 3,3′-thiodipropionate.

The amount of the sulfurized olefin may be that amount to provide 0.5 to7, percent by weight sulfur to the composition, or 0.4 to 1.5, or 1.5 to2, or 3 to 5, or 2 to 3 percent by weight. The actual amount of thesulfurized olefin may depend on the sulfur content thereof, as may bereadily calculated. If a sulfurized olefin contains 40 weight percentsulfur, as an example, the total amounts may be 1.2 to 17 weightpercent, or 1 to 3.8, or 3.8 to 5, or 7.5 to 12, or 5 to 7.5 weightpercent.

A sulfurized olefin composition may be prepared as described below.

Example S-I

A sulfurized olefin is prepared by reacting sulfur, hydrogen sulfide,and diisobutylene. Thus, 128 grams of sulfur (4 moles) is charged to ajacketed high pressure reactor which is fitted with an agitator andinternal cooling coil. Refrigerated brine is circulated through thecoils to cool the reactor prior to the introduction of the gaseousreactants. After sealing the reactor, evacuating to a pressure of lessthan 0.5 kPa and cooling, 224 grams (2 moles) of diisobutylene and 34grams (1 mole) of hydrogen sulfide are charged to the reactor.

The reactor is then heated using steam in the external jacket to atemperature of about 171° C. over about 1.5 hours. A maximum pressure of8600 kPa is reached at about 168° C. during the heat-up step. Prior toreaching the reaction temperature, the pressure starts to decrease andcontinues to decrease steadily as the gaseous reactants are consumed.

After about 10 hours at a reaction temperature of about 171° C., thepressure is approximately 2100-2200 kPa and the rate of pressure drop isabout 30-70 kPa per hour. At this time the reaction is essentiallycomplete and the unreacted hydrogen sulfide and diisobutylene are ventedto a recovery system. After the pressure of the reactor has decreased toambient, the sulfurized mixture is recovered as a liquid. The mixture isthen blown with nitrogen and vacuum stripped to remove the low boilingmaterials including unreacted diisobutylene, mercaptans, andmonosulfides. The residue is the desired sulfurized composition whichwill contain approximately 40% sulfur by weight.

Other materials may also be present in, or may be absent from, thedisclosed lubricant compositions. One such material may be a detergentwhich may optionally be an overbased detergent such as an overbasedalkaline earth metal detergent. Detergents are typically overbasedmaterials, otherwise referred to as overbased or superbased salts, whichare generally homogeneous Newtonian systems having by a metal content inexcess of that which would be present for neutralization according tothe stoichiometry of the metal and the detergent anion. The amount ofexcess metal is commonly expressed in terms of metal ratio, that is, theratio of the total equivalents of the metal to the equivalents of theacidic organic compound. Overbased materials are prepared by reacting anacidic material (such as carbon dioxide) with an acidic organiccompound, an inert reaction medium (e.g., mineral oil), a stoichiometricexcess of a metal base, and a promoter such as a phenol or alcohol. Theacidic organic material will normally have a sufficient number of carbonatoms, to provide oil-solubility.

Overbased detergents may be characterized by Total Base Number (TBN,ASTM D2896), the amount of strong acid needed to neutralize all of thematerial's basicity, expressed as mg KOH per gram of sample. Sinceoverbased detergents are commonly provided in a form which containsdiluent oil, for the purpose of this document, TBN is to be recalculatedto an oil-free basis. Some useful detergents may have a TBN of 100 to800, or 150 to 750, or, 400 to 700.

The metal compounds useful in making the basic metal salts are generallyany Group 1 or Group 2 metal compounds (CAS version of the PeriodicTable of the Elements). Examples include alkali metals such as sodium,potassium, lithium, copper, magnesium, calcium, barium, zinc, andcadmium. In one embodiment the metals are sodium, magnesium, or calcium.The anionic portion of the salt can be hydroxide, oxide, carbonate,borate, or nitrate.

In one embodiment the lubricant can contain an overbased sulfonatedetergent. Suitable sulfonic acids include hydrocarbyl-substitutedsulfonic and thiosulfonic acids, including mono- or polynuclear aromaticor cycloaliphatic compounds. In one embodiment the sulfonate detergentmay be a predominantly linear alkylbenzenesulfonate detergent having ametal ratio of at least 8 as described in paragraphs [0026] to [0037] ofUS Patent Application 2005065045.

Another overbased material is an overbased phenate detergent. Thephenols useful in making phenate detergents can be represented by(R¹)_(a)—Ar—(OH)_(b), where R¹ is an aliphatic hydrocarbyl group of 4 to400 or 6 to 80 or 6 to 30 or 8 to 25 or 8 to 15 carbon atoms; Ar is anaromatic group such as benzene, toluene or naphthalene; a and b are eachat least one, the sum of a and b being up to the number of displaceablehydrogens on the aromatic nucleus of Ar, such as 1 to 4 or 1 to 2.Phenate detergents are also sometimes provided as sulfur-bridgedspecies.

In one embodiment, the overbased material is an overbased saligenindetergent. Overbased saligenin detergents are commonly overbasedmagnesium salts which are based on saligenin derivatives. Saligenindetergents are disclosed in greater detail in U.S. Pat. No. 6,310,009,with special reference to their methods of synthesis (Column 8 andExample 1) and preferred amounts of the various species of X and Y(Column 6).

Salixarate detergents are overbased materials that can be represented bya compound comprising at least one unit of formula (I) or formula (II)and each end of the compound having a terminal group of formula (III) or(IV):

such groups being linked by divalent bridging groups A, which may be thesame or different. In formulas (I)-(IV) R³ is hydrogen, a hydrocarbylgroup, or a valence of a metal ion; R² is hydroxyl or a hydrocarbylgroup, and j is 0, 1, or 2; R⁶ is hydrogen, a hydrocarbyl group, or ahetero-substituted hydrocarbyl group; either R⁴ is hydroxyl and R⁵ andR⁷ are independently either hydrogen, a hydrocarbyl group, orhetero-substituted hydrocarbyl group, or else R⁵ and R⁷ are bothhydroxyl and R⁴ is hydrogen, a hydrocarbyl group, or ahetero-substituted hydrocarbyl group; provided that at least one of R⁴,R⁵, R⁶ and R⁷ is hydrocarbyl containing at least 8 carbon atoms.Salixarate derivatives and methods of their preparation are described ingreater detail in U.S. Pat. No. 6,200,936 and PCT Publication WO01/56968. It is believed that the salixarate derivatives have apredominantly linear, rather than macrocyclic, structure, although bothstructures are intended to be encompassed by the term “salixarate.”

Glyoxylate detergents are similar overbased materials which are based onan anionic group which may be the condensation product of ahydroxyaromatic material such as a hydrocarbyl-substituted phenol with acarboxylic reactant such as glyoxylic acid or another omega-oxoalkanoicacid. Overbased glyoxylic detergents and their methods of preparationare disclosed in greater detail in U.S. Pat. No. 6,310,011 andreferences cited therein.

The overbased detergent can also be an overbased salicylate, e,g., analkali metal or alkaline earth metal salt of a substituted salicylicacid. The salicylic acids may be hydrocarbyl-substituted wherein eachsubstituent contains an average of at least 8 carbon atoms persubstituent and 1 to 3 substituents per molecule. The substituents canbe polyalkene substituents. In one embodiment, the hydrocarbylsubstituent group contains 7 to 300 carbon atoms and can be an alkylgroup having a molecular weight of 150 to 2000. Overbased salicylatedetergents and their methods of preparation are disclosed in U.S. Pat.Nos. 4,719,023 and 3,372,116.

Other overbased detergents can include overbased detergents having aMannich base structure, as disclosed in U.S. Pat. No. 6,569,818.

In certain embodiments, the hydrocarbyl substituents onhydroxy-substituted aromatic rings in the above detergents (e.g.,phenate, saligenin, salixarate, glyoxylate, or salicylate) are free ofor substantially free of C₁₂ aliphatic hydrocarbyl groups (e.g., lessthan 1%, 0.1%, or 0.01% by weight of the substituents are C₁₂ aliphatichydrocarbyl groups). In some embodiments such hydrocarbyl substituentscontain at least 14 or at least 18 carbon atoms.

In certain embodiments an overbased alkaline earth metal detergent mayoptionally be present, in an amount to provide 0 to 500, or 10 to 100,or 1 to 50 parts per million of the alkaline earth metal or metals. Incertain embodiments the lubricant is substantially free from overbasedalkaline earth metal detergent or substantially free from all alkalineearth metal detergent, that is, the amount of the alkaline earth metalprovided thereby may be less than 5 or 3 or 1 or 0.5 parts per millionor may be zero parts per million.

Another material that optionally may be present, or that may be absent,is a polymeric viscosity index modifier. Viscosity modifiers (VM) anddispersant viscosity modifiers (DVM) are well known. Examples of VMs andDVMs may include polymethacrylates, polyacrylates, polyolefins,styrene-maleic ester copolymers, alpha-olefin-maleic ester copolymers,and similar polymeric substances including homopolymers, copolymers, andgraft copolymers. The DVM may comprise a nitrogen-containingmethacrylate polymer, for example, a nitrogen-containing methacrylatepolymer derived from methyl methacrylate and dimethylaminopropyl amine.

Examples of commercially available VMs, DVMs and their chemical typesmay include the following: polyisobutylenes (such as Indopol™ from BPAmoco or Parapol™ from ExxonMobil); olefin copolymers (such as Lubrizol®7060, 7065, and 7067 from Lubrizol and Lucant® polymers, includingethylene/propylene copolymers, including Lucant® HC-2000L and HC-600also from Lubrizol); hydrogenated styrene-diene copolymers (such asShellvis™ 40 and 50, from Shell and LZ® 7308, and 7318 from Lubrizol);styrene/maleate copolymers, which are dispersant copolymers (such as LZ®3702 and 3715 from Lubrizol); polymethacrylates, some of which havedispersant properties (such as those in the Viscoplex™ series fromRohMax, such as Viscoplex™ 0-050, the Hitec™ series of viscosity indeximprover from Afton, and LZ® 7702, 7706, 7727, 7720C, 8420, and VL9205Ffrom Lubrizol); olefin-graft-polymethacrylate polymers (such asViscoplex™ 2-500 and 2-600 from RohMax); and hydrogenated polyisoprenestar polymers (such as Shellvis™ 200 and 260, from Shell). Also includedare Asteric™ polymers from Lubrizol (methacrylate polymers with radialor star architecture). Viscosity modifiers that may be used aredescribed in U.S. Pat. Nos. 5,157,088, 5,256,752 and 5,395,539. The VMsand/or DVMs may be used in the lubricant at concentrations of 0 to 30percent by weight, or 3 to 25, or 5 to 20, or 5 to 15 weight percent.

Additional conventional components may be used in preparing a lubricantaccording to the disclosed technology, for instance, those additivestypically employed in a gear lubricant. Gear lubricants may typicallycontain any or all of the following components hereinafter described;alternatively, any one or more of the following components mayoptionally be omitted.

One additive is a dispersant. Dispersants are well known in the field oflubricants and include primarily what is known as ashless-typedispersants and polymeric dispersants. Ashless type dispersants arecharacterized by a polar group attached to a relatively high molecularweight hydrocarbon chain. Typical ashless dispersants includenitrogen-containing dispersants such as N-substituted long chain alkenylsuccinimides, also known as succinimide dispersants. Succinimidedispersants are more fully described in U.S. Pat. Nos. 4,234,435 and3,172,892. Another class of ashless dispersant is high molecular weightesters, prepared by reaction of a hydrocarbyl acylating agent and apolyhydric aliphatic alcohol such as glycerol, pentaerythritol, orsorbitol. Such materials are described in more detail in U.S. Pat. No.3,381,022. Another class of ashless dispersant is Mannich bases. Theseare materials which are formed by the condensation of a higher molecularweight, alkyl substituted phenol, an alkylene polyamine, and an aldehydesuch as formaldehyde and are described in more detail in U.S. Pat. No.3,634,515. Other dispersants include polymeric dispersant additives,which are generally hydrocarbon-based polymers which contain polarfunctionality to impart dispersancy characteristics to the polymer.Dispersants can also be post-treated by reaction with any of a varietyof agents. Among these are urea, thiourea, dimercaptothiadiazoles,carbon disulfide, aldehydes, ketones, carboxylic acids,hydrocarbon-substituted succinic anhydrides, nitriles, epoxides, boroncompounds, and phosphorus compounds. References detailing such treatmentare listed in U.S. Pat. No. 4,654,403. The amount of dispersant in thepresent composition can typically be 1 to 10 weight percent, or 1.5 to9.0 percent, or 2.0 to 8.0 percent, all expressed on an oil-free basis.

Another component is an antioxidant. Antioxidants encompass phenolicantioxidants, which may comprise a butyl substituted phenol containing 2or 3 t-butyl groups. The para position may also be occupied by ahydrocarbyl group, an ester-containing group, or a group bridging twoaromatic rings. Antioxidants also include aromatic amine, such asnonylated diphenylamines or alkylated phenylnaphthylamine. Otherantioxidants include sulfurized olefins, titanium compounds, andmolybdenum compounds. U.S. Pat. No. 4,285,822, for instance, discloseslubricating oil compositions containing a molybdenum and sulfurcontaining composition. U.S. Patent Application Publication 2006-0217271discloses a variety of titanium compounds, including titanium alkoxidesand titanated dispersants, which materials may also impart improvementsin deposit control and filterability. Other titanium compounds includetitanium carboxylates such as neodecanoate. Typical amounts ofantioxidants will, of course, depend on the specific antioxidant and itsindividual effectiveness, but illustrative total amounts can be 0.01 to5 percent by weight or 0.15 to 4.5 percent or 0.2 to 4 percent.Additionally, more than one antioxidant may be present, and certaincombinations of these can be synergistic in their combined overalleffect.

Another additive is an antiwear agent, other than those that have beendescribed above. Examples of anti-wear agents includephosphorus-containing antiwear/extreme pressure agents such as metalthiophosphates, phosphoric acid esters and salts thereof,phosphorus-containing carboxylic acids, esters, ethers, and amides; andphosphites. In certain embodiments a phosphorus antiwear agent may bepresent in an amount to deliver 0.01 to 0.2, or 0.015 to 0.15, or 0.02to 0.1, or 0.025 to 0.08 percent phosphorus. The antiwear agent may be azinc dialkyldithiophosphate (ZDP). For a typical ZDP, which may contain11 percent P (calculated on an oil free basis), suitable amounts mayinclude 0.09 to 0.82 percent. Non-phosphorus-containing anti-wear agentsinclude borate esters (including borated epoxides), dithiocarbamatecompounds, molybdenum-containing compounds, and sulfurized olefins.

Other materials that may be used as antiwear agents include tartrateesters, tartramides, and tartrimides. Examples include oleyl tartrimide(the imide formed from oleylamine and tartaric acid) and oleyl diesters(from, e.g., mixed C12-16 alcohols). Other related materials that may beuseful include esters, amides, and imides of other hydroxy-carboxylicacids in general, including hydroxy-polycarboxylic acids, for instance,acids such as tartaric acid, citric acid, lactic acid, glycolic acid,hydroxy-propionic acid, hydroxyglutaric acid, and mixtures thereof.These materials may also impart additional functionality to a lubricantbeyond antiwear performance. These materials are described in greaterdetail in US Publication 2006-0079413 and PCT publication WO2010/077630.Such derivatives of (or compounds derived from) a hydroxy-carboxylicacid, if present, may typically be present in the lubricatingcomposition in an amount of 0.1 weight % to 5 weight %, or 0.2 weight %to 3 weight %, or greater than 0.2 weight % to 3 weight %.

Other additives that may optionally be used in lubricating oils includepour point depressing agents, extreme pressure agents, anti-wear agents,color stabilizers, and anti-foam agents.

The amount of each chemical component described is presented exclusiveof any solvent or diluent oil, which may be customarily present in thecommercial material, that is, on an active chemical basis, unlessotherwise indicated. However, unless otherwise indicated, each chemicalor composition referred to herein should be interpreted as being acommercial grade material which may contain the isomers, by-products,derivatives, and other such materials which are normally understood tobe present in the commercial grade.

As used herein, the term “hydrocarbyl substituent” or “hydrocarbylgroup” is used in its ordinary sense, which is well-known to thoseskilled in the art. Specifically, it refers to a group having a carbonatom directly attached to the remainder of the molecule and havingpredominantly hydrocarbon character. Examples of hydrocarbyl groupsinclude:

hydrocarbon substituents, that is, aliphatic (e.g., alkyl or alkenyl),alicyclic (e.g., cycloalkyl, cycloalkenyl) substituents, and aromatic-,aliphatic-, and alicyclic-substituted aromatic substituents, as well ascyclic substituents wherein the ring is completed through anotherportion of the molecule (e.g., two substituents together form a ring);

substituted hydrocarbon substituents, that is, substituents containingnon-hydrocarbon groups which, in the context of this invention, do notalter the predominantly hydrocarbon nature of the substituent (e.g.,halo (especially chloro and fluoro), hydroxy, alkoxy, mercapto,alkylmercapto, nitro, nitroso, and sulfoxy);

hetero substituents, that is, substituents which, while having apredominantly hydrocarbon character, in the context of this invention,contain other than carbon in a ring or chain otherwise composed ofcarbon atoms and encompass substituents as pyridyl, furyl, thienyl andimidazolyl. Heteroatoms include sulfur, oxygen, and nitrogen. Ingeneral, no more than two, or no more than one, non-hydrocarbonsubstituent will be present for every ten carbon atoms in thehydrocarbyl group; alternatively, there may be no non-hydrocarbonsubstituents in the hydrocarbyl group.

It is known that some of the materials described above may interact inthe final formulation, so that the components of the final formulationmay be different from those that are initially added. For instance,metal ions (of, e.g., a detergent) can migrate to other acidic oranionic sites of other molecules. The products formed thereby, includingthe products formed upon employing the composition of the presentinvention in its intended use, may not be susceptible of easydescription. Nevertheless, all such modifications and reaction productsare included within the scope of the present invention; the presentinvention encompasses the composition prepared by admixing thecomponents described above.

The invention herein is useful for imparting wear performance to alubricant such as a gear lubricant formulation, which may be betterunderstood with reference to the following examples.

Examples

Typical gear lubricant formulations are prepared in low KV_100formulations. Details of the formulations are presented in the Tablebelow. All amounts are on an oil-free (active chemical) basis except forthe commercial anti-foam agent(s) which are reported as providedcommercially (believed to contain 65-90% oil).

Ex. (ID # for reference) 1* 2* 3* 4 5 6 7 8 295 296 298 316 348 349 351353 Poly alpha olefin oil, 77.2 77.2 77.2 75.5 75.5 75.5 75.5 75.5KV_100 = 4 mm²/s Amine salt of — — — 1.66 0.83 0.50 0.65 1.25 Pcompound^(a) di-C18 alkyl phosphite 0.5 0.5 0.5 0.8 0.5 0.5 0.5 0.4di-C8 alkyl phosphate, 1.3 1.3 1.5 0.8 1.0 1.0 1.0 0.4 C8 amine salt % Pin composition 0.128 0.126 0.143 0.224 0.176 0.148 0.157 0.160Sulfurized C4 olefins 4.2 4.6 4.2 4.1 4.1 4.1 4.1 4.0 (44% S) % S incomposition 1.85 2.02 1.85 1.80 1.80 1.80 1.80 1.76 KV_100 ofcomposition 5.9 5.9 5.9 6.0 6.0 6.0 6.0 6.0 Additional components Esterpolymer viscosity 12.5 12.5 12.5 12.5 12.5 12.5 12.5 12.5 modifierCorrosion inhibitors 0.7 0.7 0.7 0.65 0.65 0.65 0.65 0.65 Borateddispersant 0.67 0.67 0.67 0.72 1.00 1.00 1.00 1.00 Antifoam agents 0.070.07 0.07 0.02 0.02 0.02 0.02 0.02 Ester of hydroxy acid 0.08 0.11 0.110.08 0.08 0.08 0.10 0.10 Friction modifier(s)^(c) 0.04 0.04 0.04 0.320.32 0.32 0.12 0.12 Wear test results L-37 ring gear wear rating 7 7 79/8 9 9 9 9 (ASTM D6121) *a reference or comparative example^(a)obtained by reacting phosphorus pentasulfide alcohol of 4-8 carbonatoms, with an alkylene oxide and further with phosphorus pentoxide, andsalting the resulting material with amine having 12 to 24 carbon atoms.^(b)long chain amine, amide, and/or imidazoline compounds ^(c)Thefriction modifiers are non-phosphorus-containing materials. It is knownto those skilled in the art that L-37 test performance depends on thepresence of phosphorus-containing component(s). The minor variations inthe amount or composition of the friction modifiers will not affect theL-37 wear results.

The results show that the presence of the amine salt of the phosphoruscompound provides improved wear performance compared with the otherphosphorus compounds, in a low viscosity lubricant formulation.

Another series of examples were prepared in relatively low and in highviscosity formulations. The formulations are summarized in the tablebelow:

Ex. (ID # for reference) 9* (390) 10* (739) 11 (391) 12* (770) Low visc.High visc. Low visc. High visc. Group II base oil, 91 91 6 mm²/s Group Ibase oil, 77.4 77.4 12 mm²/s Bright stock, 31 mm²/s 13.6 13.6 Amine saltof 1.16 1.16 P compound^(a) Di-C8 alkyl phosphate, 0.85 0.85 C8 aminesalt Dialkyl phosphite 0.42 0.42 anti-wear agents Sulfurized olefin 3.23.2 3.2 3.2 (45% S) Borated dispersant 0.59 0.59 0.59 0.59 Othercomponents 1.54 1.54 1.86 1.86 including friction modifier, corrosioninhibitors, pour point depressant Diluent oil Balance to = 100% KV_100of the 6.12 13.12 6.09 13.1 composition *A comparative or referenceexample ^(a)obtained by reacting phosphorus pentasulfide alcohol of 4-8carbon atoms, with an alkylene oxide and further with phosphoruspentoxide, and salting the resulting material with amine having 12 to 24carbon atoms.

The formulations of Examples 9-12 are subjected to the L-37 test (ASTMD6121). The results, including the pass criteria, are shown in the tablebelow:

Ex.: Test value (pass criterion) 9* 10* 11 12* Final ring gear wear (>5)8 7 7 8 Final ring gear surface 9 9 9 10 fatigue rippling (>8) Finalring gear surface 9 10 10 10 fatigue ridging (>8) Final ring gearsurface fatigue 9.9 9.9 9.9 9.9 pitting/spalling (>9.3) Final ring gearsurface 10 10 10 10 fatigue scoring (>9.3) Final pinion gear wear (>5) 67 7 8 Final pinion gear rippling (>8) 8.7 9.4 9.4 9 Final pinion gearsurface 7.3 8 8 10 ridging (>8) Final pinion gear pitting/spalling 9.99.9 9.9 9.9 merit (>9.3) Final pinion gear scoring (>9.3) 10 10 10 10

The result show that, using the formulations of examples 9-12, both thecompositions of the disclosed technology and the reference compositionsmeet all the passing criteria when used in a high viscosity formulation(10 and 12). However, in the low viscosity formulations (9 and 11), theformulation containing the amine phosphorus salt disclosed herein meetsall the passing criteria, while the formulation containing thealternative phosphorus compound does not meet at least one of thepassing criteria.

Each of the documents referred to above is incorporated herein byreference, including any prior applications, whether or not specificallylisted above, from which priority is claimed. The mention of anydocument is not an admission that such document qualifies as prior artor constitutes the general knowledge of the skilled person in anyjurisdiction. Except in the Examples, or where otherwise explicitlyindicated, all numerical quantities in this description specifyingamounts of materials, reaction conditions, molecular weights, number ofcarbon atoms, and the like, are to be understood as optionally modifiedby the word “about.” It is to be understood that the upper and loweramount, range, and ratio limits set forth herein may be independentlycombined. Similarly, the ranges and amounts for each element of theinvention can be used together with ranges or amounts for any of theother elements.

As used herein, the transitional term “comprising,” which is synonymouswith “including,” “containing,” or “characterized by,” is inclusive oropen-ended and does not exclude additional, un-recited elements ormethod steps. However, in each recitation of “comprising” herein, it isintended that the term also encompass, as alternative embodiments, thephrases “consisting essentially of” and “consisting of,” where“consisting of” excludes any element or step not specified and“consisting essentially of” permits the inclusion of additionalun-recited elements or steps that do not materially affect the essentialor basic and novel characteristics of the composition or method underconsideration. The expression “consisting of” or “consisting essentiallyof,” when applied to an element of a claim, is intended to restrict allspecies of the type represented by that element, notwithstanding thepresence of “comprising” elsewhere in the claim.

While certain representative embodiments and details have been shown forthe purpose of illustrating the subject invention, it will be apparentto those skilled in this art that various changes and modifications canbe made therein without departing from the scope of the subjectinvention. In this regard, the scope of the invention is to be limitedonly by the following claims.

1. A lubricant composition comprising: (a) about 40 to about 95 percentby weight, or about 58 to about 80 percent by weight, of an oil having akinematic viscosity at 100° C. by ASTM D445 of about 3 to about 7.5, orabout 3.6 to about 6, or about 3.5 to about 5 mm^(2/)s; (b) about 0.3 toabout 2 percent by weight of an amine salt of a phosphorus compound, ormixtures thereof, obtained by reacting phosphorus pentasulfide with oneor more alcohols having 4 to about 13, or 4 to 8, or 6, carbon atoms,with an alkylene oxide, and further with phosphorus pentoxide, andsalting the resulting material with one or more amines having 2 to 20 or12 to 24 carbon atoms; and (c) a sulfurized olefin in an amount toprovide about 0.5 to about 7, or about 0.5 to about 1.5, or about 1.5 toabout 2, or about 3 to about 5, or about 2 to about 3, percent by weightsulfur to the composition; wherein said composition has a kinematicviscosity at 100° C. by ASTM D445 of up to about 7.5 mm²/s.
 2. Thelubricant composition of claim 1 wherein the oil comprises a polyalphaolefin having a kinematic viscosity at 100° C. of about 3 to about 7.5.3. The lubricant composition of claim 1 wherein the oil comprises an APIGroup III oil or a Group III+ oil.
 4. The lubricant composition of claim1 wherein the alkylene oxide comprises 1,2-propylene oxide.
 5. Thelubricant composition of claim 1 wherein the alcohol has 6 carbon atoms.6. The lubricant composition of claim 1 wherein the alcohol is4-methylpentan-2-ol.
 7. The lubricant composition of claim 1 having aphosphorus content of or about 0.02 to about 0.20 weight percentphosphorus supplied by the material of component (b).
 8. The lubricantcomposition of claim 1 wherein the total phosphorus content of thelubricant is about 0.08 to about 0.30 weight percent.
 9. The lubricantcomposition of claim 1 further comprising an overbased alkaline earthmetal detergent in an amount to provide 1 to about 500 50 parts bymillion by weight alkaline earth metal.
 10. The lubricant composition ofclaim 1 being substantially free from alkaline earth metal detergent.11. The lubricant composition of claim 1 further comprising 5 to about30 percent by weight of a polymeric viscosity index modifier.
 12. Acomposition prepared by admixing the components of claim
 1. 13. A methodof lubricating a gear or a bearing, comprising supplying thereto thelubricant composition of claim
 1. 14. The method of claim 13 comprisinglubricating a gear wherein the gear is located in an axle assembly. 15.The method of claim 13 comprising lubricating a gear wherein the gear isa hypoid gear.
 16. The method of claim 13 wherein the lubricantcomposition is employed in a lubricated axle assembly characterized by aλ value of less than 2.0, or 1.1 to 1.5, where λ is defined as the ratioof elastohydrodynamic film thickness of the lubricant to the compositesurface roughness of the gear surface.